The present invention relates to apparatus for transporting discrete articles or commodities or groups of articles or commodities which form part of or constitute smokers' products. More particularly, the invention relates to improvements in apparatus for transporting rod-shaped, sheet-like or otherwise configurated articles which form part of or constitute smokers' products between a first transfer station to which the articles are delivered or fed by a first conveyor and a second transfer station at which the articles are accepted by a further conveyor. Still more particularly, the invention relates to improvements in apparatus wherein the articles are transported by a hollow rotary drum-shaped cylindrical conveyor and are attracted to the periphery of the drum-shaped conveyor by establishment of a pressure differential during transport from the first to the second transfer station. Articles which can be transported by the improved apparatus may constitute plain or filter tipped cigarettes, cheroots, cigars or cigarillos and/or one or more constituents of such smokers' products, e.g., filter rod sections, plain cigarettes, cigars or cigarillos, or adhesive-coated uniting bands which are used to connect filter plugs to tobacco-containing rod-shaped articles in a filter tipping machine. Furthermore, the articles may constitute component parts of packets for cigarettes or the like.
It is known to transport rod-shaped constituents of smokers' products in the peripheral flutes of a rotary drum-shaped conveyor wherein the flutes communicate with a suction chamber by way of suction ports which are machined into the shell or body of the conveyor. Such transport insures gentle treatment of articles and predictable delivery of articles to a further conveyor or the like at the second transfer station.
In a modern plant for the manufacture and/or processing of smokers' products, all or at least some machines are often connected to a common suction generating device. When the machines are arrested, e.g., at the end of a day's shift, it is customary to operate the machines until the last article or articles are removed from various conveyors or the like. If a machine includes one or more rotary drum-shaped conveyors of the type to which the present invention pertains, such conveyors or conveyors will be operated until all of the suction ports are exposed so that atmospheric air is free to enter the respective suction chamber by way of each and every suction port in the conveyor. When a machine embodying one or more suction-operated conveyors is to be started again, it is often difficult or impossible to immediately attract the articles to the periphery of the rotary conveyor or conveyors because the pressure differential is too low owing to the fact that all of the suction ports communicate with the atmosphere as well as with the suction chamber or chambers. As a rule, the suction generating device is dimensioned and adjusted in such a way that its capacity suffices to generate requisite suction under normal operating conditions, namely, when the majority of suction ports are sealed from the atmosphere by articles which are transported from the first to the second transfer station. Thus, such conventional transporting apparatus begin to operate satisfactorily only when a substantial number of suction ports between the two transfer stations are already overlapped by articles. This insures that the suction in ports between the two transfer stations suffices to adequately retain the articles on the rotating conveyor. It is neither practical nor economical to design the suction generating device in such a way that it can adequately attract a single article, a small number of articles or a maximum number of articles between the two transfer station. In addition to its higher cost, such suction generating device is undesirable or impractical because the filters which are integrated into the suction generating system between the suction ports and the suction generating device are normally designed to furnish a satisfactory filtering action only when the suction matches or closely approximates a predetermined value, namely, that pressure differential which prevails in normal operation when all or nearly all suction ports between the two transfer stations are overlapped by articles. The provision of auxiliary suction generating devices which are actuated when the machine embodying a transporting apparatus of the type to which the present invention pertains is to be set in motion is equally undesirable because the auxiliary devices contribute to initial and maintenance cost of the equipment. Moreover, it is normally necessary to provide the machine or machines with complex controls which automatically start one or more auxiliary suction generating devices when the pressure differential between the suction chamber or chambers and the surrounding atmosphere is too low.
British patent No. 1,078,229 discloses a transporting apparatus wherein a hollow cylindrical drum-shaped article-transporting conveyor surrounds and rotates with respect to a stationary core. The latter has a relatively narrow channel which extends between the two transfer stations and establishes direct communication between the inner ends of suction ports in the conveyor and a suction chamber in the core. The channel throttles the flow of air from the atmosphere into the suction chamber when one or more suction ports are not overlapped by articles. However, such narrow channel is often clogged by dust, fragments of tobacco or other foreign matter so that the maintenance cost of the patented apparatus is relatively high and the number and duration of down times is also high. Removal of foreign matter from the channel is a complex and time-consuming procedure.
Another transporting apparatus is disclosed in U.S. Pat. No. 3,901,373 granted Aug. 26, 1975 to Willy Rudszinat. This apparatus includes a stationary core which has an arcuate channel whose upstream and downstream ends communicate with the suction chamber. The channel is located radially inwardly of suction ports in the rotary cylindrical conveyor. Air which enters the channel via one or more suction ports must flow toward the one or the other end of the channel prior to admission into the suction chamber. It has been found that such apparatus cannot insure a satisfactory or reliable self-cleaning action because particles of dust, tobacco or the like are apt to remain in the channel in spite of the fact that the outer side of the channel is bounded by the moving internal surface of the cylindrical conveyor. During travel toward the one or the other end of the channel, particles of foreign matter are likely to accumulate in the channel and to form clots which exert an adverse influence upon suction in the ports of the rotating conveyor. Moreover, the pressure differential between the atmosphere and the suction chamber is too low to guarantee reliable retention of articles at the outer ends of suction ports which communicate with the channel of the core whenever a substantial number of ports between the two transfer stations are free to communicate with the atmosphere.